Ever heard of Rotoscoping? Even if you haven't heard of it, I'm certain you've seen it. It's an animation technique used to trace live-action footage to turn it ointo a cartoon. The most "famous" uses of rotoscoping is the A-HA video "Take On Me", the movie "Snow Wite and the Seven Dwarves", Fleischer Studio's "Superman" cartoons from the 1940s... oh, and the tremendously awful 1978 "Lord of the Rings" cartoon.

From Wikipedia:"Rotoscoping is an animation technique in which animators trace over footage, frame by frame, for use in live-action and animated films.[1] Originally, recorded live-action film images were projected onto a frosted glass panel and re-drawn by an animator. This projection equipment is called a rotoscope, although this device has been replaced by computers in recent years. In the visual effects industry, the term rotoscoping refers to the technique of manually creating a matte for an element on a live-action plate so it may be composited over another background."